Plasma processing apparatus

ABSTRACT

A uniformity of plasma density in a target object surface and plasma processing characteristics can be improved. A plasma processing apparatus  10  includes: a processing chamber  100  in which a plasma process is performed on a wafer W; a first high frequency power supply  140  configured to output a high frequency power; a high frequency antenna  120  including an outer coil, an inner coil and n (n is an integer equal to or greater than 1) number of intermediate coil(s) that are concentrically wound about a central axis outside the processing chamber  100 ; and a dielectric window  105  provided at a part of a wall of the processing chamber  100  and configured to introduce electromagnetic field energy generated from the high frequency antenna  120  into the processing chamber  100.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No. 2009-0086470 filed on Mar. 31, 2009, and U.S. Provisional Application Ser. No. 61/186,921 filed on Jun. 15, 2009, the entire disclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates to a plasma processing apparatus performing a plasma process on a target object; and, more particularly, to a high frequency antenna to be used therein.

BACKGROUND OF THE INVENTION

As examples of apparatuses that perform microprocessing on a target object by exciting plasma, there are a capacitively coupled plasma processing apparatus, an inductively coupled plasma (ICP) processing apparatus, a microwave plasma processing apparatus, and the like. Among them, the ICP processing apparatus includes a high frequency antenna installed at a dielectric window provided on a ceiling surface of a processing chamber. In such an ICP processing apparatus, an electromagnetic field is generated around a coil of the antenna by a high frequency current applied to the coil, and the electric field energy is introduced into the processing chamber through the dielectric window. As a result, a gas is excited into plasma by the electric field energy (see, for example, Patent Document 1).

In Patent Document 1, the high frequency antenna has a planar shape, and it includes two spiral coils, i.e., an inner spiral coil and an outer spiral coil. A power is split and supplied to the two spiral coils, and, thus, a density distribution of the inductively coupled plasma generated within the processing chamber can be adjusted.

Patent Document 1: Japanese Patent Laid-open Publication No. 2007-311182

In the high frequency antenna having the above-described configuration, however, two donut-shaped plasma are generated by currents of circular pattern flowing through the two inner and outer coils, and a plasma density between the two donut-shaped plasma decreases. As a result, plasma process uniformity in a target object surface deteriorates. Besides, since the plasma density also varies depending on plasma conditions such as pressure or the like, it has been difficult to achieve plasma uniformity.

Especially, as the size of the target object is larger, the size of the plasma processing apparatus is larger. Accordingly, plasma needs to be generated uniformly over a wide plasma excitation region within the large-sized plasma processing apparatus. Therefore, it has been more difficult to achieve the plasma uniformity.

BRIEF SUMMARY OF THE INVENTION

In view of the foregoing, the present disclosure provides a plasma processing apparatus capable of improving uniformity of plasma density and plasma processing characteristics in the target object surface.

In order to solve the above-mentioned problem, in accordance with one aspect of the present disclosure, there is provided a plasma processing apparatus including a processing chamber in which a plasma process is performed on a target object; a first high frequency power supply configured to output a high frequency power; a high frequency antenna including an outer coil, an inner coil and n (n is an integer equal to or greater than 1) number of intermediate coil(s) that are concentrically wound about a central axis outside the processing chamber; and a dielectric window provided at a part of a wall of the processing chamber and configured to introduce electromagnetic field energy generated from the high frequency antenna into the processing chamber.

In accordance with this configuration, the high frequency antenna includes the outer coil, the inner coil and the n (n is an integer equal to or greater than 1) number of intermediate coils between them that are concentrically wound about the central axis. As a result, plasma can be generated in a plasma excitation region by the n (n≧1) number of intermediate coils as well as the inner coil and the outer coil. Accordingly, it is possible to avoid a decrease of a plasma density, which would occur in an intermediate region between the inner and the outer coils if the plasma is generated by the two coils, i.e., the inner and outer coils. Therefore, overall plasma uniformity can be achieved, so that uniformity of the plasma process in the target object surface can be secured.

The plasma processing apparatus may further include a power splitter provided at least between the outer coil and the inner coil and configured to split the high frequency power outputted from the first high frequency power supply at a desired ratio and supply the split power to each coil.

For example, a high frequency power of a highest power level is supplied to the outer coil, and a high frequency power of a power level lower than that is supplied to the inner coil. Then, the rest high frequency power is supplied to the intermediate coil.

The plasma density tends to decrease on a peripheral side of the target object because electrons or ions in the plasma diffuse into a wall of a processing chamber and disappear. In consideration of this tendency, the high frequency power of the highest power level is applied to the outer coil so as to allow a highest plasma density at the peripheral side. Accordingly, a decrease of an etching rate at an edge portion of the target object can be suppressed, for example. The rest of the high frequency power split by the power splitter is split again to be supplied to the inner coil and the intermediate coil.

As a consequence, a plasma density at an outer region of the plasma excitation region is controlled to be slightly higher than an overall plasma density, while a plasma density decreases at an intermediate region between the outer region and the inner region of the plasma excitation region is suppressed. Therefore, the overall plasma uniformity can be achieved, so that the uniformity of the plasma process in the target object surface can be secured.

In the plasma processing apparatus, the power splitter may be provided between the respective coils and be configured to split the high frequency power outputted from the first high frequency power supply at a desired ratio and supply the split power to each coil.

In the plasma processing apparatus, at least one of the coils may be movably configured so as to vary a distance from the dielectric window.

In the plasma processing apparatus, in case that the power splitter is not provided between two coils, one of the two coils may be movably configured.

In the plasma processing apparatus, the two or more power splitters may be symmetrically arranged with respect to the central axis.

In the plasma processing apparatus, the two or more power splitters may be asymmetrically arranged with respect to the central axis, and a space in which the power splitters may be positioned and a space in which the high frequency antenna is positioned may be shielded by a shield member.

In the plasma processing apparatus, each of the outer coil, the inner coil and the intermediate coil may be formed of a plurality of coils; power feed points of the coils forming the outer coil may be arranged at symmetrical positions with respect to the central axis; power feed points of the coils forming the intermediate coil may be arranged at symmetrical positions with respect to the central axis; and power feed points of the coils forming the inner coil may be arranged at symmetrical positions with respect to the central axis.

In the plasma processing apparatus, the power feed points of the coils may be arranged at an angular interval of about 180°, 120°, 90°, 72° or 60°.

In the plasma processing apparatus, a blocking capacitor may be coupled to each coil.

In the plasma processing apparatus, the two or more power splitters may have variable capacitors.

The plasma processing apparatus may further include: a measuring unit configured to measure at least one of a current, a voltage and a phase of a high frequency power supplied to each coil; and a control unit configured to control the ratio of the power split by the power splitter based on at least one of the current, the voltage and the phase of the high frequency power measured by the measuring unit.

In the plasma processing apparatus, the control unit may include a memory and control the ratio of the power split by the power splitter according to a recipe previously stored in the memory.

The plasma processing apparatus may further include: a second high frequency power supply configured to output a high frequency power; and a power splitter configured to split the high frequency power outputted from the second high frequency power supply at a desired ratio. Furthermore, one of the outer coil, the inner coil and the intermediate coil may be connected to the first high frequency power supply, the rest two coils, which are not connected with the first high frequency power supply, may be connected to the second high frequency power supply, and the power splitter may supply the split power to the rest two coils.

In the plasma processing apparatus, the first high frequency power supply may be connected to the outer coil, and the second high frequency power supply may be connected to the inner coil and the intermediate coil.

The plasma processing apparatus may further include: a second high frequency power supply and a third high frequency power supply configured to output high frequency powers. Further, one of the outer coil, the inner coil and the intermediate coil may be connected to the first high frequency power supply, and one of the rest two coils, which is not connected with the first high frequency power supply, may be connected to the second high frequency power supply, while the other one of the rest two coils may be connected to the third high frequency power supply.

In accordance with the present disclosure, uniformity of plasma density and plasma processing characteristics in the target object surface can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may best be understood by reference to the following description taken in conjunction with the following figures:

FIG. 1 is a longitudinal cross sectional view of a plasma processing apparatus in accordance with a first embodiment of the present disclosure;

FIG. 2 is a diagram illustrating a configuration of a high frequency antenna in accordance with the first embodiment;

FIG. 3A is a graph showing plasma density in a wafer diametric direction, and FIG. 3B is a graph for describing an operation of a blocking capacitor;

FIG. 4 is an equivalent circuit in accordance with the first embodiment;

FIG. 5 is a diagram illustrating a modification example of the plasma processing apparatus in accordance with the first embodiment;

FIG. 6 is a diagram illustrating another modification example of the plasma processing apparatus in accordance with the first embodiment;

FIG. 7 is a diagram illustrating still another modification example of the plasma processing apparatus in accordance with the first embodiment;

FIG. 8A is a longitudinal cross sectional view of a plasma processing apparatus in accordance with a second embodiment of the present disclosure, and FIG. 8B is a diagram illustrating a configuration of a high frequency antenna in accordance with the second embodiment;

FIG. 9 is a graph illustrating a voltage state in a wafer circumferential direction;

FIG. 10 is a longitudinal cross sectional view of a plasma processing apparatus in accordance with a third embodiment of the present disclosure;

FIG. 11A is a longitudinal cross sectional view of a plasma processing apparatus in accordance with a fourth embodiment of the present disclosure, and FIG. 11B is a diagram illustrating a configuration of a high frequency antenna in accordance with the fourth embodiment;

FIG. 12 is a longitudinal cross sectional view of a plasma processing apparatus in accordance with a fifth embodiment of the present disclosure; and

FIG. 13 is a longitudinal cross sectional view of a plasma processing apparatus in accordance with a sixth embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Through the whole document, same parts having substantially the same function and configuration will be assigned same reference numerals, and redundant description thereof will be omitted.

First Embodiment Overall Configuration of Plasma Processing Apparatus

Referring to FIGS. 1 and 2, an overall configuration of a plasma processing apparatus in accordance with a first embodiment of the present disclosure will be explained. FIG. 1 is a schematic longitudinal cross sectional view of an inductively coupled plasma processing apparatus, and FIG. 2 is a diagram illustrating a configuration of a high frequency antenna.

As shown in FIG. 1, a plasma processing apparatus 10 such as an etching apparatus includes a processing chamber 100 for plasma-processing a wafer W which is loaded through a gate valve GV. The processing chamber 100 having a cylindrical shape is made of metal such as aluminum, and is grounded. An inner wall of the processing chamber 100 is anodically oxidized. Further, the inner wall of the processing chamber 100 may be covered with a dielectric material such as quartz, yttria, or the like.

A dielectric window 105 is fitted into an opening of the processing chamber 100 at a ceiling surface of the processing chamber 100, and, thus, a space within the processing chamber 100 is hermetically sealed. The dielectric window 105 is configured as a circular plate made of, e.g., alumina or quartz. The dielectric window 105 transmits electromagnetic field energy generated from a high frequency antenna 120 and introduces the energy into the processing chamber 100.

A shower plate 110 is provided in a bottom surface of the dielectric window 105. The shower plate 110 is provided with a gas inlet pipe 110 a. The gas inlet pipe 110 a discharges a gas into the processing chamber 100 through a multiple number of gas holes 110 b opened toward the wafer W. The gas inlet pipe 110 a is connected with a gas supply source 115 by penetrating outward through a center of the ceiling surface of the processing chamber 100.

A high frequency (RF) antenna 120 is provided on the atmospheric side of the dielectric window 105. As illustrated in FIG. 2, a surface of the dielectric window 105 is divided into three imaginary zones: an outer zone, an inner zone, and an intermediate zone. Further, an axis passing a center of the dielectric window 105 is denoted by a central axis O.

The high frequency antenna 120 includes an outer coil 120 a provided in the outer zone, an inner coil 120 c provided in the inner zone and an intermediate coil 120 b provided in the intermediate zone. The outer coil 120 a, the intermediate coil 120 b and the inner coil 120 c are arranged concentrically with respect to the central axis O.

Further, in the present embodiment, although the coils 120 a to 120 c are wound substantially one round in the respective zones, they may be wound multiple rounds. Further, although only one intermediate zone is provided in the present embodiment, the intermediate zone may be divided into two or more, and intermediate coils may be provided in the respective intermediate zones in one-to-one correspondence.

One ends of the coils 120 a to 120 c are connected with power feed rods 125 a to 125 c, respectively. The power feed rods 125 a to 125 c are coupled to a first high frequency power supply 140 via a matching unit 135. A high frequency power outputted from the first high frequency power supply 140 is applied to the coils 120 a to 120 c through the matching unit 135 and the power feed rods 125 a to 125 c, respectively. As a result, high frequency currents flow through the coils 120 a to 120 c.

A power splitter 130 is provided between the coils 120 a to 120 c. The power splitter 130 includes variable impedance circuits (e.g., variable capacitors) 130 a and 130 b. An outer antenna circuit includes only the outer coil 120 a. An intermediate antenna circuit includes the variable impedance circuit 130 a and the intermediate coil 120 b, and an inner antenna circuit includes the variable impedance circuit 130 a, the variable impedance circuit 130 b and the inner coil 120 c.

The variable impedance circuits 130 a and 130 b function as impedance adjustment units. That is, by adjusting a capacitance of the variable impedance circuit 130 a, impedance of the intermediate and the inner antenna circuits can be adjusted, and, thus, a ratio between a current flowing to the outer antenna circuit and a current flowing to the intermediate and the inner antenna circuits can be controlled, as will be described later. Likewise, by adjusting a capacitance of the variable impedance circuit 130 b, the impedance of the intermediate antenna circuit and the inner antenna circuit is adjusted, and, thus, a ratio between a current flowing to the intermediate antenna circuit and a current flowing to the inner antenna circuit can be controlled.

As stated above, the variable impedance circuits 130 a and 130 b have a power split function of supplying a high frequency power outputted from the first high frequency power supply 140 to the respective coils after splitting the high frequency power at a desired power ratio. Further, the variable capacitor may be installed only between the outer coil 120 a and the inner coil 120 c, but if the variable capacitors are installed all between the respective coils, as in the present embodiment, accuracy of the power split control can be more improved.

In the above configuration, a high frequency power of, e.g., about 13.56 MHz is supplied from the first high frequency power supply 140 to the high frequency antenna 120 during a plasma process. Thus, high frequency currents flow through the coils 120 a to 120 c of the high frequency antenna 120. As a result, electromagnetic fields are generated around the coils, and the electric field energy is introduced into the processing chamber 100 through the dielectric window 105. The introduced electric field energy excites a gas into plasma. Here, a density distribution of the plasma is controlled by adjusting the impedance of the outer coil 120 a, the intermediate coil 120 b and the inner coil 120 c by means of the variable impedance circuits 130 a and 130 b, as will be described later in further detail.

The other ends of the outer coil 120 a, the intermediate coil 120 b and the inner coil 120 c are grounded via blocking capacitors 145 a to 145 c, respectively. The function of the blocking capacitors 145 a to 145 c will be described later.

A mounting table 150 configured to mount the wafer W thereon is provided within the processing chamber 100. The wafer W mounted on the mounting table 150 is attracted to and held on an electrostatic chuck (not shown). The mounting table 150 is connected with a high frequency bias power supply 160 via a matching unit 155. The high frequency bias power supply 160 is configured to apply a high frequency bias power having a frequency of, e.g., about 2 MHz to the mounting table 150 during a plasma process. Ions in the plasma generated in the processing chamber 100 are effectively attracted to the wafer W by this high frequency bias power.

A gas exhaust unit 170 having a vacuum pump is connected to a bottom portion of the processing chamber 100 via a gas exhaust pipe 165, and is configured to evacuate the inside of the processing chamber 100 to a predetermined vacuum level of, e.g., about 1.33 Pa.

The power splitter 130 is connected with a control unit 220. The control unit 220 includes a CPU 220 a, a memory 220 b, and an interface (I/F) 220 c. In the control unit 220, signals can be transceived between the respective parts via an internal bus 220 d.

The memory 220 b stores recipes for adjusting the capacitances of the variable impedance circuits 130 a and 130 b of the power splitter 130. In the recipes, capacitances of the variable impedance circuits 130 a and 130 b for respective processes are predetermined. The CPU 220 a selects a recipe corresponding to a process to be performed and adjusts the capacitances of the variable impedance circuits 130 a and 130 b according to the selected recipe. The recipes may be stored in a hard disk, a storage medium such as a CD-ROM, or the like, or the recipes may be appropriately downloaded through a network.

(Antenna Configuration)

For example, if a high frequency antenna includes two spiral coils, i.e., an outer spiral coil and an inner spiral coil, two donut-shaped plasma are generated from currents of circular pattern flowing through the two spiral coils, and density of the plasma between the two donut-shaped plasma decreases. For example, a curve Np in FIG. 3A shows an example plasma density distribution created by the two spiral coils. A plasma density is high at an outer portion and an inner portion of the wafer W having a diameter of 300 mm, while the plasma density between the outer portion and the inner portion decreases. As a result, plasma processing uniformity in the wafer surface may be deteriorated, resulting in a reduction of yield and productivity.

In contrast, in the high frequency antenna 120 in accordance with the present embodiment, the three spiral coils, i.e., the outer coil 120 a, the intermediate coil 120 b and the inner coil 120 c are concentrically wound about the central axis O. Accordingly, a plasma density distribution as indicated by a curve Nc of FIG. 3A is created by the three spiral coils, i.e., the outer coil 120 a, the intermediate coil 120 b and the inner coil 120 c. In the plasma density distribution, a plasma density is high at the outer portion and the inner portion of the wafer, and it does not decrease between them owing to the presence of the intermediate coil 120 b. As a result, the plasma processing uniformity in the wafer surface improves, resulting in an increase of the yield and the productivity.

Especially, it is expected that a plasma process would be performed on a wafer having a diameter of about 450 mm later, although a wafer having a diameter of about 300 mm is mainly used as the target object at present. Further, sizes of FPD substrates are getting larger year by year, and a plasma process will be also performed on these substrates. Accordingly, it will become more important to achieve plasma uniformity on large areas in order to increase of the yield and the productivity. In the present embodiment, the number n (n≧1) of intermediate coils may increase according to a size of a target object. In this way, the shape of the high frequency antenna 120 can be appropriately determined lest the plasma density between the inner portion and the outer portion of the wafer decrease.

(Power Split/Impedance Adjustment)

Further, the high frequency power applied to the respective coils is split by the power splitter 130 at a desired ratio. An impedance adjustment function of the high frequency antenna 120 will be explained below with reference to FIG. 4.

FIG. 4 shows an equivalent circuit of a power feed part of the high frequency antenna 120. As stated above, the high frequency power outputted from the first high frequency power supply 140 is supplied to the outer coil 120 a, the intermediate coil 120 b and the inner coil 120 c via the matching unit 135. The high frequency power is directly supplied to the outer coil 120 a. Meanwhile, the high frequency power is supplied to the intermediate coil 120 b via the variable impedance circuit (e.g., variable capacitor) 130 a and to the inner coil 120 c via the variable impedance circuit (e.g., variable capacitor) 130 a and the variable impedance circuit (e.g., variable capacitor) 130 b.

A method for adjusting impedances Zo, Zc, Zi of the outer coil 120 a, the intermediate coil 120 b and the inner coil 120 c will be discussed. Since the outer coil 120 a includes only the coil, its impedance Zo has a fixed value. The impedance Zc of the intermediate coil 120 b can be varied by changing a capacitance of the variable impedance circuit 130 a. The impedance Zi of the inner coil 120 c can be varied by changing a capacitance of the variable impedance circuits 130 a and 130 b.

High frequency currents Ii, Ic and Io vary according to a ratio between the impedances Zi, Zc and Zo. Based on this relationship, the capacitances of the variable impedance circuits 130 a and 130 b are individually adjusted in response to instructions from the control unit 220. By varying the impedances Zi and Zc in this way, the ratio between the impedances Zi, Zc and Zo can be changed. As a result, a ratio between the high frequency currents Ii, Ic and Io flowing through the respective coils can be controlled.

The plasma density tends to decrease on a peripheral side of the wafer W because electrons or ions in the plasma collide with a wall and are disappeared. In consideration of this tendency, a high frequency power of a highest power level is applied to the outer coil 120 a so as to achieve a highest plasma density at the peripheral side. The rest of the high frequency power split by the power splitter 130 is divided again and supplied to the inner coil 120 c and the intermediate coil 120 b. In this way, by using the three coils 120 a to 120 c of the high frequency antenna 120 and the power splitter 130, an inductively coupled state between the high frequency antenna 120 and the plasma can be adjusted. As a result, a plasma density at an outer side of a plasma excitation region can be controlled to be slightly higher than an overall plasma density, and a plasma density decreases in an intermediate portion between the outer side and an inner side of the plasma excitation region can be suppressed. Thus, the overall plasma uniformity can be improved, so that the plasma processing uniformity in the target object can be maintained.

Recently, there is a user's demand for performing multiple kinds of processes in a single chamber. So far, however, it has been difficult to secure plasma uniformity because the plasma uniformity varies depending on, e.g., a kind of a gas, a pressure, and an RF power for each plasma process. Meanwhile, in the plasma processing apparatus in accordance with the present embodiment, power can be appropriately supplied depending on the kinds of plasma processes by performing the power split control on the antenna having the three or more zones. Thus, plasma uniformity can be secured for each process.

(Feedback Control)

The control unit 220 may perform a feedback control of the ratio between the high frequency powers applied to the respective coils. In such a case, measuring units 250 a, 250 b and 250 c are coupled to the power feed rods 125 a, 125 b and 125 c, respectively, so as to measure at least one of a phase, a voltage and a current of a high frequency power flowing through each of the coils 120 a, 120 b and 120 c.

The control unit 220 is configured to control the power ratio split by the power splitter 130 based on phases, voltages and/or currents of a high frequency power measured by the measuring units 250 a to 250 c. To elaborate, the control unit 220 calculates the high frequency power applied to each of the coils 120 a to 120 c based on the phase, the voltage and/or the current of a high frequency power flowing through each coil. Here, the high frequency power is calculated based on an equation P=VI×cos θ (V: voltage, I: current, θ: phase). Then, the control unit 220 performs a feedback control of the variable impedance circuits 130 a and 130 b so as to reduce a difference between a target high frequency power supposed to be applied to each of the coils 120 a to 120 c and a currently inputted power. The measuring units 250 a to 250 c may be voltmeters, probes or CTs (Current Transfer).

Through the above-described feedback control, non-uniformity of the plasma density can be corrected from the state of the curve Np to the state of the curve Nc and then to the state of the curve Nu (Np→Nc→Nu) as shown in FIG. 3A. Thus, more uniform plasma can be generated.

Furthermore, the control unit 220 may include the memory 220 b, and it may control the power split ratio by the power splitter 130 according to recipes previously stored in the memory 220 b. In such a case, a plurality of recipes for controlling the power ratio split by the power splitter 130 is previously stored in the memory 220 b, and capacitances of the variable impedance circuits 130 a and 130 b are previously set in the recipes. The CPU 220 a selects a recipe corresponding to a target process to be performed and controls the capacitances of the variable impedance circuits 130 a and 130 b according to the selected recipe.

In the inductively coupled plasma processing apparatus, symmetry of the apparatus is important to uniformly supply the electric field energy to the plasma because the high frequency electromagnetic field is used to generate the plasma. Accordingly, in the present embodiment, the variable impedance circuits 130 a and 130 b are arranged on the central axis O of the apparatus in series, and symmetry of the variable impedance circuits 130 a and 130 b and the high frequency antenna 120 including the three spiral coils in the three zones is maintained, as illustrated in FIGS. 1 and 2. That is, the high frequency antenna 120 has symmetry with respect to the central axis O, and the power splitter 130 also exhibits symmetry with respect to the central axis O.

(Blocking Capacitors)

The blocking capacitors 145 a to 145 c are coupled to the end portions of the coils 120 a to 120 c, respectively. Referring to FIG. 3B, in case of using the blocking capacitors 145 a to 145 c, a voltage V_(p2) at each of power feed points Sa, Sb and Sc of the coils 120 a, 120 b and 120 c can be reduced to about the half of a voltage V_(p1) at each of the power feed points Sa, Sb and Sc of the coils 120 a, 120 b and 120 c when the blocking capacitors 145 a to 145 c are not used. Accordingly, a ceiling plate in the vicinity of the power feed points Sa, Sb and Sc can be suppressed from being severely sputtered by accelerated electrons.

Modification Examples of the First Embodiment

Modification examples of the first embodiment are illustrated in FIGS. 5 to 7. Although the inside configuration of a processing chamber 100 is not illustrated in each plasma processing apparatus 10 shown in FIGS. 5 to 7, the inside configuration of the processing chamber 100 is the same as shown in FIG. 1. In a plasma processing apparatus 10 of FIG. 5, a power feed point Sc of an inner coil 120 c is deviated about 180° from power feed points Sa and Sb of an outer coil 120 a and an intermediate coil 120 b, respectively. In a plasma processing apparatus 10 of FIG. 6, power feed points Sb and Sc of an intermediate coil 120 b and an inner coil 120 c are deviated about 180° from a power feed point Sa of an outer coil 120 a.

In a plasma processing apparatus 10 of FIG. 7, a power feed point Sc of an inner coil 120 c is deviated about 180° from power feed points Sa and Sb of an outer coil 120 a and an intermediate coil 120 b, respectively. Here, the variable impedance circuits 130 a and 130 b are connected in series in FIGS. 5 and 6, whereas the variable impedance circuits 130 a and 130 b are connected in parallel in FIG. 7. In both cases, however, they are symmetrical with respect to the central axis O.

In accordance with the modification examples, plasma uniformity can be improved by supplying a high frequency power to the high frequency antenna 120 having the three or more zones after splitting the power appropriately.

Second Embodiment

Generally, in the inductively coupled plasma processing apparatus, not only (1) the generation of the plasma by acceleration of electrons using the electromagnetic field energy from the high frequency antenna 120 needs to be considered, but (2) plasma uniformity also needs to be achieved in consideration of electrons coupled to the plasma by a capacitor. Thus, the apparatus needs to be designed in consideration of not only an antenna design for (1) but also a capacitive component for (2).

In the plasma processing apparatus 10 in accordance with the first embodiment, uniformity of a plasma density in a diametric direction of the wafer W can be achieved. That is, in the first embodiment, the high frequency antenna 120 is divided into the three imaginary zones, i.e., the outer zone, the inner zone and the intermediate zone, and the above-mentioned coils are installed in the respective zones in consideration of (1), so that the uniformity of the plasma density in the diametric direction can be improved.

Furthermore, in the first embodiment, by using the blocking capacitors in consideration of (2), the voltage at each power feed point can be reduced. As a result, the dielectric window 105 in the vicinity of the power feed points can avoid attack by the plasma due to high voltages at the power feed points.

In a second embodiment, plasma uniformity in a circumferential direction of the wafer W is additionally achieved. By arranging a plurality of power feed points symmetrically, the plasma density in the circumferential direction can be improved in the second embodiment.

When a single coil is wound one round or more in a high frequency antenna, the high frequency antenna has an unsymmetrical voltage distribution in a circumferential direction. FIG. 9 shows a distribution of a voltage V_(p1) of a coil wound one round) (360°. Here, the voltage V_(p1) is highest at a power feed point P, and then it decreases gradually. Accordingly, a plasma density in a circumferential direction is highest at the power feed point P, and then it decreases gradually. As can be seen from this result, uniformity of the plasma density in the circumferential direction cannot be achieved by winding the single coil only one round.

In the second embodiment, in order to solve this problem, the uniformity of the plasma density in the circumferential direction can be accomplished by providing two spiral coils in each zone. FIG. 8A is a schematic longitudinal cross sectional view of a plasma processing apparatus 10 in accordance with the second embodiment. In this plasma processing apparatus 10, the inside of a processing chamber 100 has the same configuration as shown in FIG. 1, though not shown. FIG. 8B schematically illustrates a power feed part of the plasma processing apparatus 10 in accordance with the second embodiment.

Two outer coils, i.e., a first outer coil 120 a 1 and a second outer coil 120 a 2 are arranged in an outer zone. One ends of the first and second outer coil 120 a 1 and 120 a 2 are connected to power feed rods 125 a 1 and 125 a 2 at power feed points Sa1 and Sa2, respectively. A high frequency power outputted from a first high frequency power supply 140 is applied to the first and second outer coils 120 a 1 and 120 a 2 through the matching unit 135, the power feed rods 125 a 1 and 125 a 2, respectively. The first outer coil 120 a 1 and the second outer coil 120 a 2 are grounded via blocking capacitors 145 a 1 and 145 a 2, respectively, after wound one round about a central axis O in the same direction. The power feed points Sa1 and Sa2 are arranged at facing positions with respect to the central axis O while spaced apart from each other at an angular interval of about 180°.

Referring back to FIG. 9, the graph also shows a distribution of a voltage V_(p11) of the first outer coil 120 a 1 and a distribution of a voltage V_(p12) of the second outer coil 120 a 2 when the two spiral coils are wound one round) (360°. Here, the voltages V_(p11) and V_(p12) of the two spiral coils are highest at the power feed points Sa1 and Sa2, respectively, and then they decrease gradually. However, the voltages V_(p11) and V_(p12) at the power feed points Sa1 and Sa2 are lower than the voltage V_(p1) at the power feed point P when only the single coil is used. Additionally, the power feed points Sa1 and Sa2 are spaced apart from each other at an angular interval of about 180°. Accordingly, electromagnetic field energy generated around the two outer coils 120 a 1 and 120 a 2 becomes more uniform in the circumferential direction than electromagnetic field energy generated around the single coil.

Likewise, two intermediate coils, i.e., a first intermediate coil 120 b 1 and a second intermediate coil 120 b 2 are arranged in an intermediate zone. One ends of the first intermediate coil 120 b 1 and the second intermediate coil 120 b 2 are connected to power feed rods 125 b 1 and 125 b 2 at power feed points Sb1 and Sb2, respectively. The high frequency power outputted from the first high frequency power 140 is applied to the first and the second intermediate coils 120 b 1 and 120 b 2 through the power feed rods 125 b 1 and 125 b 2, respectively. The first and the second intermediate coils 120 b 1 and 120 b 2 are grounded via blocking capacitors 145 b 1 and 145 b 2 after they are wound one round.

Likewise, two inner coils, i.e., a first inner coil 120 c 1 and a second inner coil 120 c 2 are arranged in an inner zone. One ends of the first and second inner coils 120 c 1 and 120 c 2 are connected to power feed rods 125 c 1 and 125 c 2 at power feed points Sc1 and Sc2, respectively. The high frequency power outputted from the first high frequency power supply 140 is applied to the first and the second inner coils 120 c 1 and 120 c 2 through the power feed rods 125 c 1 and 125 c 2. The first and the second inner coils 120 c 1 and 120 c 2 are grounded via blocking capacitors 145 c 1 and 145 c 2 after they are wound one round.

In case that the single coil is wound only one round, the uniformity of the plasma density in the circumferential direction cannot be achieved. In the second embodiment, however, by winding the two spiral coils in the same direction and arranging the power feed points of the spiral coils at the angular interval of about 180°, voltage uniformity improves in the circumferential direction of the two spiral coils as shown in FIG. 9, so that uniformity of an electric field energy introduced into the processing chamber 100 can be improved. As a result, attack force on a dielectric window 105 in the vicinity of the power feed points can be reduced, and the uniformity of plasma density in the circumferential direction can be improved for each zone.

Additionally, in the second embodiment, uniformity of plasma density in a diametric direction can also be achieved by providing at least three zones and splitting power, as described in the first embodiment. In the plasma processing apparatus 10 in accordance with the second embodiment, more uniform plasma can be generated in an entire plasma excitation region, and, thus, it is possible to cope with the scale up of the plasma processing apparatus.

Moreover, desirably, each of the outer coil, the inner coil and the intermediate coil may be formed of a plurality of coils, respectively, and power feed points of the plurality of coils forming the outer coil may be provided at symmetrical positions with respect to the central axis O. For example, in the high frequency antenna 120 of the second embodiment, the coils start from two points and are wound one round and then grounded, and the two power feed points are symmetrical at an angular interval of about 180°. However, it may be also possible to provide three power feed points symmetrically at an angular interval of about 120° or to provide four power feed points symmetrically at an angular interval of about 90°.

The power feed points of each coil may be arranged at any one angular interval of about 180°, 120°, 90°, 72° or 60°. As the number of symmetrically arranged power feed points increases, the uniformity of the plasma density in the circumferential direction improves, resulting in reduction of attack force on the dielectric window 105 in the vicinity of the power feed points. Further, as the number of the power feed points increases, not only plasma distribution uniformity dependent on an electromagnetic field distribution but also plasma distribution uniformity dependent on a capacitance distribution can be more improved.

Third Embodiment

In the first embodiment, the variable impedance circuits (e.g., variable capacitors) 130 a and 130 b in the power splitter 130 are symmetrically arranged with respect to the central axis O. In contrast, in a third embodiment, variable impedance circuits 130 a and 130 b are asymmetrically arranged with respect to a central axis O. In this case, a space in which a power splitter 130 is positioned and a space in which a high frequency antenna 120 is positioned are shielded by a shield member 300 as illustrated in FIG. 10. The shield member 300 is made of a conductive material such as aluminum. The high frequency antenna 120 is accommodated in an antenna room 310.

With this configuration, asymmetric coupling of the power splitter 130 and the high frequency antenna 120 can be avoided, and, symmetry of stray capacitance components can be maintained. As a result, a magnetic field state near the antenna can be prevented from being affected by plasma generation. Furthermore, by suppressing interference of an electric field between the power splitter 130 and the high frequency antenna 120, the balance of amplitude, voltage, or the like in the antenna can be maintained.

Fourth Embodiment

In a fourth embodiment, plasma coupling is controlled by varying a distance between a high frequency antenna 120 and plasma. In FIGS. 11A and 11B, a power splitter 130 includes only one variable impedance circuit 130 a that splits power between an outer coil 120 a 2 and an intermediate coil 120 b 2. In the present embodiment, four power feed points Sa1, Sa2, Sb1 and Sb2 are provided.

An intermediate coil 120 b 1 and an inner coil 120 c 1 are connected via a conductive wire 125 c 1. The intermediate coil 120 b 2 and an inner coil 120 c 2 are connected via a conductive wire 125 c 2. Blocking capacitors 145 a 1, 145 a 2, 145 c 1 and 145 c 2 are provided at end portions of the outer coils 120 a 1 and 120 a 2 and the inner coils 120 c 1 and 120 c 2.

The inner coils 120 c 1 and 120 c 2 are movably configured so as to vary a distance from a dielectric window 105. A space 400 is provided between the inner coils 120 c 1 and 120 c 2 and the dielectric window 105.

With this configuration, if the high frequency antenna 120 is lowered, the distance between the high frequency antenna 120 and the plasma decreases, resulting in improvement of acceleration of electrons. Meanwhile, if the high frequency antenna 120 is raised, acceleration of the electrons may be deteriorated because the distance between the high frequency antenna 120 and the plasma increases.

By adjusting the distance between the dielectric window 105 and the coils, the same effect as that achieved by varying a power ratio between the coils can be achieved. For example, by setting a distance between one coil and the plasma to be longer than a distance between other coil and the plasma, the coupling degree of the one coil with the plasma becomes smaller than the coupling degree of the other coil with the plasma even when the same current is flowing therein.

In the above description, although the inner coils 120 c 1 and 120 c 2 are configured to be movable, it may be possible to move at least one pair of the outer coils 120 a 1 and 120 a 2, the intermediate coils 120 b 1 and 120 b 2, and the inner coils 120 c 1 and 120 c 2 so as to vary the distance from the dielectric window 105. Further, all of the outer coils, the inner coils and the intermediate coils may be configured to be movable.

Furthermore, a dielectric member may be provided in the space 400 between the high frequency antenna 120 and the dielectric window 105, or the space 400 may be filled with Galden. Maintaining the distance between the high frequency antenna 120 and the dielectric window 105, providing the dielectric member between them, filling the space 400 between the high frequency antenna 120 and the dielectric window 105 with Galden, and the like are various ways to add a capacitance component as a way to vary a capacitive distribution without using a capacitor. Desirably, the provided dielectric member may have a high dielectric constant.

Moreover, by varying a thickness of the dielectric member between the high frequency antenna 120 and the dielectric window 105, a plasma coupling state can be changed. A plasma distribution can be changed by a simple mechanism in this way, and, thus, a manufacturing cost of the plasma processing apparatus can be reduced.

Fifth Embodiment

In a fifth embodiment, a second high frequency power supply 141 that outputs a desired high frequency power is provided in addition to a first high frequency power supply 140, as illustrated in FIG. 12. In the present embodiment, the first high frequency power 140 is connected to an outer coil 120 a via a matching unit 135, and the second high frequency power supply 141 is connected to an inner coil 120 c and an intermediate coil 120 b via a matching unit 136. A variable impedance circuit 130 a is configured to split a high frequency power outputted from the second high frequency power supply 141 at a desired ratio and supply the split power to the inner coil 120 c and the intermediate coil 120 b.

In accordance with the fifth embodiment, in a process requiring an optimum power supply to each of three zones, controllability improves, and, thus, it is possible to split power with high accuracy.

Further, in the present embodiment, although the outer coil 120 a is connected to the first high frequency power supply 140 while the rest two coils (the inner coil 120 c and the intermediate coil 120 b) are connected to the second high frequency power supply 141, the invention is not limited to this configuration. Moreover, it is possible to connect any one of the outer coil 120 a, the inner coil 120 c and the intermediate coil 120 b to the high frequency power supply 140 while the rest two coils which are not connected with the first high frequency power supply 140 are connected to the second high frequency power supply 141.

Sixth Embodiment

In a sixth embodiment, a second and a third high frequency power supplies 141 and 142 that output a desired high frequency power are provided in addition to a first high frequency power supply 140, as illustrated in FIG. 13. In the present embodiment, the first high frequency power 140 is connected to an outer coil 120 a via a matching unit 135, and the second high frequency power supply 141 is connected to an intermediate coil 120 b via a matching unit 136, while the third high frequency power supply 142 is connected to an inner coil 120 c via a matching unit 137.

As described above, in the present embodiment, any one of the outer coil 120 a, the inner coil 120 c and the intermediate coil 120 b is connected to the first high frequency power supply 140, and one of the rest two spiral coils which are not connected with the first high frequency power supply 140 is connected to the second high frequency power supply 141, while the other one of the rest two spiral coils is connected to the third high frequency power supply 142.

In accordance with the sixth embodiment, in a process requiring an optimum power supply to each of three zones, controllability improves, and, thus, it is possible to split power with high accuracy.

As described above, in accordance with the embodiments of the present disclosure, a high frequency power is inputted to the antenna having the three or more zones while varying a power input ratio by means of the variable capacitor(s). Accordingly, the power supplied to each winding coil is split, and plasma uniformity in the diametric direction of the wafer W can be achieved.

Moreover, by providing a plurality of power feed points symmetrically to the antenna (coil) in each zone, plasma uniformity in the circumferential direction of the wafer W can also be achieved. As compared to a high-price configuration in which individual power supplies are used for the respective coils, the configuration in which the power to be inputted to the respective coils is split by the power splitter 130 is more cost-effective.

Although the present disclosure has been described with respect to the embodiments in conjunction with the accompanying drawings, it is clear that the above-described embodiments are illustrative in all aspects and do not limit the present disclosure. The above description of the present disclosure is provided for the purpose of illustration, and it would be understood by those skilled in the art that various changes and modifications may be made without changing technical conception and essential features of the present disclosure as defined in the following claims.

Further, it shall be understood that all modifications and embodiments conceived from the meaning and scope of the claims and their equivalents are included in the scope of the present disclosure.

For example, as for the winding number of the coil(s) in each zone of the high frequency antenna in accordance with the present disclosure, each coil may be wound two or more round on a same plane or may be arranged vertically.

Although not illustrated, when a gas is discharged into the processing chamber, a flow rate or a kind of the gas may be controlled in concentric multiple zones including the outer zone, the inner zone and the intermediate zone.

Further, the plasma processing apparatus is not limited to the etching apparatus, but it can be any kind of processing apparatus performing a plasma process such as asking, surface modification, or CVD (Chemical Vapor Deposition).

Furthermore, the target object to be processed by the plasma processing apparatus in accordance with the present disclosure is not limited to the silicon wafer. For example, the target object may be a substrate for FPD (Flat Panel Display), a substrate for a solar cell, or the like. Examples of the FPD may be a liquid crystal display (LCD), a light emitting diode (LED) display, an electroluminescence (EL) display, a vacuum fluorescent display (VFD), a plasma display panel (PDP), and the like. 

1. A plasma processing apparatus comprising: a processing chamber in which a plasma process is performed on a target object; a first high frequency power supply configured to output a high frequency power; a high frequency antenna including an outer coil, an inner coil and n (n is an integer equal to or greater than 1) number of intermediate coil(s) that are concentrically wound about a central axis outside the processing chamber; and a dielectric window provided at an opening of the processing chamber and configured to introduce electromagnetic field energy generated from the high frequency antenna into the processing chamber.
 2. The plasma processing apparatus of claim 1, further comprising: a power splitter provided at least between the outer coil and the inner coil and configured to split the high frequency power outputted from the first high frequency power supply at a desired ratio and supply the split power to each coil.
 3. The plasma processing apparatus of claim 2, wherein the power splitter is provided between the respective coils and is configured to split the high frequency power outputted from the first high frequency power supply at a desired ratio and supply the split power to each coil.
 4. The plasma processing apparatus of claim 1, wherein at least one of the coils is movably configured so as to vary a distance from the dielectric window.
 5. The plasma processing apparatus of claim 4, wherein, in case that the power splitter is not provided between two coils, one of the two coils is movably configured.
 6. The plasma processing apparatus of claim 2, wherein the two or more power splitters are symmetrically arranged with respect to the central axis.
 7. The plasma processing apparatus of claim 2, wherein the two or more power splitters are asymmetrically arranged with respect to the central axis, and a space in which the power splitters are positioned and a space in which the high frequency antenna is positioned are shielded by a shield member.
 8. The plasma processing apparatus of claim 1, wherein each of the outer coil, the inner coil and the intermediate coil is formed of a plurality of coils; power feed points of the coils forming the outer coil are arranged at symmetrical positions with respect to the central axis; power feed points of the coils forming the intermediate coil are arranged at symmetrical positions with respect to the central axis; and power feed points of the coils forming the inner coil are arranged at symmetrical positions with respect to the central axis.
 9. The plasma processing apparatus of claim 8, wherein the power feed points of the coils are arranged at an angular interval of about 180°, 120°, 90°, 72° or 60°.
 10. The plasma processing apparatus of claim 1, wherein a blocking capacitor is coupled to each coil.
 11. The plasma processing apparatus of claim 2, wherein the two or more power splitters have variable capacitors.
 12. The plasma processing apparatus of claim 2, further comprising: a measuring unit configured to measure at least one of a current, a voltage and a phase of a high frequency power supplied to each coil; and a control unit configured to control the ratio of the power split by the power splitter based on at least one of the current, the voltage and the phase of the high frequency power measured by the measuring unit.
 13. The plasma processing apparatus of claim 12, wherein the control unit includes a memory and controls the ratio of the power split by the power splitter according to a recipe previously stored in the memory.
 14. The plasma processing apparatus of claim 1, further comprising: a second high frequency power supply configured to output a high frequency power; and a power splitter configured to split the high frequency power outputted from the second high frequency power supply at a desired ratio, wherein one of the outer coil, the inner coil and the intermediate coil is connected to the first high frequency power supply, the rest two coils, which are not connected with the first high frequency power supply, are connected to the second high frequency power supply, and the power splitter supplies the split power to the rest two coils.
 15. The plasma processing apparatus of claim 14, wherein the first high frequency power supply is connected to the outer coil, and the second high frequency power supply is connected to the inner coil and the intermediate coil.
 16. The plasma processing apparatus of claim 1, further comprising: a second high frequency power supply and a third high frequency power supply configured to output high frequency powers, wherein one of the outer coil, the inner coil and the intermediate coil is connected to the first high frequency power supply, and one of the rest two coils, which are not connected with the first high frequency power supply, is connected to the second high frequency power supply, while the other one of the rest two coils is connected to the third high frequency power supply. 